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  • 2000-2004  (2)
  • 1
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A highly uniform thermal x-radiation field for indirect-drive inertial confinement fusion implosions may be obtained by irradiating a four-hole, tetrahedral geometry, spherical hohlraum with all 60 Omega laser beams. Implosion studies and calculations [J. M. Wallace et al., Phys. Rev. Lett. 82, 3807 (1999)] indicate a drive uniformity comparable to that expected for the National Ignition Facility [J. A. Painser et al., Laser Focus World 30, 75 (1994)]. With 60 beams distributed over the cavity wall, tetrahedral hohlraums have a natural insensitivity to power balance and pointing errors. Standard, smooth Nova capsules imploded with this drive indicate that moderate convergence-ratio implosions, Cr∼18, have measured-neutron yield to calculated-clean-one-dimensional-neutronyield ratios similar to those previously investigated using the comparatively poor drive uniformity of Nova cylindrical hohlraums. This may indicate that a nonsymmetry-related neutron yield degradation mechanism, e.g., hydrodynamic mixing of cold, dense ablator material with the hot-spot region or some combination of nonsymmetry effects, is dominating in this Cr regime. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 657-662 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Z-Beamlet laser backlighter system at Sandia National Laboratories, which will be operational in 2001, will create a point or area source of high (or moderate) energy x rays behind a Z-accelerator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] -driven target. In the former case with 〉2 kJ in up to four pulses of 〈2 ns total duration in a 20 ns interval, and 〉80% of the 2ω energy in a ∼50-μm-diam focal spot, the resulting 〉4×1016 W/cm2 irradiances will generate ≥8.950, 8.999 keV (zinc He-α, etc.) x rays. This high-energy source, as either a single point or four separate spots, will be used directly for four-frame point-projection x-ray imaging, and will attain spatial resolutions and signal-to-noise levels significantly better than presently possible on Z using existing methods. In combination with a ∼1 cm field of view, the technique will be well suited to the large, relatively opaque objects characteristic of Z experiments. This addition is anticipated to have a major impact upon the basic physics of z-pinch implosions, and therefore, possibly the ultimate x-ray powers and hohlraum (vacuum or dynamic) radiation temperatures that may be attainable. Furthermore, in combination with a slightly defocused point source and a medium-energy grazing-incidence microscope, Z-Beamlet may allow various inertial confinement fusion and high-energy-density physics experiments to be studied at even higher spatial resolution and signal-to-noise levels. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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